A voice coil motor is configured to drive lenses along an optical axis in image capturing devices thereby achieving an auto-focus function of the image capturing device. A typical voice coil motor includes a moveable frame for accommodating a lens barrel with lenses therein, a wire coil wrapped around the moveable frame, a number of magnets, a stationary frame for fixing the magnets and accommodating the moveable frame.
When a current is applied to the coil, a magnetic force is produced between the magnets and the wire coil, and the moveable frame with the lens barrel moves upward relative to the stationary frame. When the current is cut off, the moveable frame with the lens barrel is reset to its original position. However, during the movement of the moveable frame, the magnetic force must overcome pre-stress first. This causes a large current and wastes electricity.
Therefore, it is desirable to provide a voice coil motor, which can overcome or at least alleviate the above-mentioned problems.